1. Field of the Invention
The present invention relates to a sheet delivery device of a sheet-fed press of the type that sheets being conveyed to a sheet stacker portion from a printing machine portion are provisionally received so that the sheets can be stably and continuously stacked.
2. Description of the Prior Art
With reference to FIGS. 7 and 8, a sheet delivery device of a general sheet-fed press in the prior art will be described. Also, with reference to FIGS. 9 and 10, a sheet stacker portion as a main part of the sheet delivery device will be described.
FIG. 7 is a schematic entire construction explanatory view of one example of a prior art sheet-fed press. FIG. 8 is an explanatory view of a prior art sheet stacking method and comprises FIGS. 8(a) and 8(b), wherein FIG. 8(a) is of a continuous stacking system and FIG. 8(b) is of a divided stacking system. FIG. 9 is an explanatory view of the continuous stacking system of FIG. 8(a) and comprises FIGS. 9(a) and 9(b), wherein FIG. 9(a) is a construction explanatory side view of main portions thereof and FIG. 9(b) is a view seen from arrows E—E of FIG. 9(a). FIG. 10 is an explanatory view of the divided stacking system of FIG. 8(b) and comprises FIGS. 10(a) and 10(b), wherein FIG. 10(a) is a construction explanatory side view of main portions thereof and FIG. 10(b) is a view seen from arrows F—F of FIG. 10(a).
While there are various types of the sheet-fed press, the example shown in FIG. 7 is constructed by such main devices and portions (constructing elements) as a sheet feeder 20, printing machine 17, sheet delivery device 1 portion, etc. The sheet delivery device 1 portion comprises a sheet conveyor 2 and sheet stacker 3.
Functions of the respective devices and portions will be briefly described. The sheet feeder 20 is a device that has sheets 6 to be printed stacked on a sheet feeding table 21 and supplies the sheets 6 one after another into the printing machine 17 as the next step.
The printing machine 17 comprises a plurality of printing devices (17a to 17d), arrayed in parallel to each other, in the number corresponding to the kinds of inks, such as of black, blue, red, yellow or other specific colors, as needed. While the sheets 6 supplied one after another from the sheet feeder 20 are being sequentially conveyed downstream via claw-like members provided on impression cylinders 18 (18a to 18d) and intermediate cylinders 22, the inks of the necessary colors are transferred onto the sheets 6. That is, in each of the printing devices, the ink of a necessary quantity is prepared by an inking device to be supplied onto a press plate 24 fitted to a plate cylinder 23. The ink transferred onto picture or letter portions of the press plate 24 is further transferred onto a rubber cylinder 25 and the ink on the outer circumferential surface of the rubber cylinder 25 is transferred onto each of the sheets 6 that is being conveyed between the rubber cylinder 25 and the impression cylinder 18. It is to be noted that the illustration of FIG. 7 shows an example of the sheet-fed press constructed having four printing devices 17a to 17d on the upper side of the sheet path line so that printing of four colors can be carried out on the surface of each of the sheets 6 and the number of the printing devices can be variously set.
The sheets 6 on which the first color has been printed at the first press device 17a are conveyed to the first intermediate cylinder 22 from the first impression cylinder 18a to be received on the second impression cylinder 18b of the second printing device 17b. Then, the sheets 6 pass through the third and fourth (last) printing devices 17c, 17d and the aimed multi-color printing is completed.
The sheets 6 on which a predetermined printing has been completed are conveyed to the downstream sheet delivery device 1 portion from the impression cylinder 18d of the last printing device 17d by the sheet conveyor 2. The sheet conveyor 2 comprises an endless chain 9 that runs being wound around a sheet delivery axle 19 and a chain gripper 10 is provided on the endless chain 9. The printed sheets 6 are received to be held by the chain gripper 10 and are conveyed in this state. Above a sheet delivery table 26, and at an appropriate position (timing) in the sheet running direction, the sheets 6 are released from the chain gripper 10 by a sheet release cam (not shown) and fall down one after another on a pallet 4 placed on the sheet delivery table 26 to be stacked thereon.
At this time, front ends of the printed sheets 6 conveyed by the sheet conveyor 2 abut on a front abutting member 7 provided on the downstream upper side of the sheet stacker 3 portion so that the front ends of the sheets 6 are arrayed and in this state, the sheets 6 are stacked on the pallet 4 placed on the sheet delivery table 26 of the sheet stacker 3. When the sheets 6 begin to fall down as mentioned above, their running velocity is controlled to be retarded so that damage of the sheets caused by a violent collision with the front abutting member 7 can be avoided. As a means to control the velocity of the sheets 6, a vacuum suction roller 8 is provided on an inlet upper portion of the sheet stacker 3.
This vacuum suction roller 8 is constructed having an outer roller and being supported on a frame by bearings to be rotatably driven by an independent motor (not shown) or by being connected to the printing machine portion and has an entire outer circumferential surface of the outer roller provided with a plurality of suction holes bored along the circumferential direction. The vacuum suction roller 8 is operated such that the circumferential velocity thereof is sufficiently slower than the running velocity of the sheets 6. Thus, when the sheets 6 being conveyed run on a plate-like sheet guide 5 provided below the sheet conveyor 2, their velocity is retarded by the vacuum suction roller 8 and hence the sheets 6 fall down on the sheet delivery table 26 in the state that the velocity is reduced.
The sheet delivery table 26 is controlled to be lowered corresponding to the stacked thickness of the falling sheets 6 so that the falling distance of the sheets 6 is maintained approximately constant. When a predetermined number of the sheets 6 are stacked on the pallet 4 so that a predetermined stacking condition is achieved, the pallet 4 together with the stacked sheets 6 is taken out to be conveyed outside and a vacant pallet 4 for replacement is placed on the sheet delivery table 26.
As a sheet stacking method carried out by the sheet stacker 3, there are typically a continuous stacking system shown in FIG. 8(a) and a divided stacking system shown in FIG. 8(b). In the continuous stacking system, the falling sheets 6 are continuously stacked without interruption to form a bundle of a predetermined number of sheets. This system is often employed when there are sheets of thick paper or there is printing having little ink transfer on the sheet back side.
In the continuous stacking system, as shown in FIGS. 9(a) and 9(b), the sheets 6 are continuously fed onto the pallet 4 placed on the sheet delivery table 26 until a predetermined number of the sheets 6 are stacked. When stacking of the predetermined number of the sheets 6 is attained, a shutter bar unit 12 of a shutter device 11 that has been on a stand-by position is moved and quickly inserted between the falling sheets 6 so that the subsequent sheets 6 are provisionally received on the shutter bar unit 12 and thus the sheets 6 are separated into a lower portion of the stacked sheets and an upper portion of the sheets to be subsequently stacked.
The shutter device 11 has two endless chains 15 provided on both sides of the sheet delivery table 26. These endless chains 15, as shown in FIGS. 9(a) and 9(b), are wound around a plurality of sets of sprockets 14a to 14d fitted to frames of both sides of the sheet delivery device 1 portion so as to run along the sheet conveying direction of the sheet conveyor 2. The shutter bar unit 12 comprises a plurality of roller assemblies arrayed in the running direction of the endless chains 15 and each of the roller assemblies comprises a roller 29 having its both ends rotatably supported via bearings 28 to attachments 16 fitted to predetermined portions of both of the endless chains 15.
One set of the sprockets 14a is connected to a reversible motor 27 and by the drive of the motor 27, the shutter bar unit 12 can be operated so as to move between the operation position [shown by double-dotted chain lines in FIG. 9(a)] that is above the stacked sheets 6 and below a front end portion of the sheet conveyor 2 and the stand-by position [shown by solid lines in FIG. 9(a)] that is apart from the operation position.
As mentioned above, after the sheets 6 are provisionally received to be separated by the shutter bar unit 12 at the operation position, the sheet delivery table 26 is lowered to stop at the lowermost position and the bundle of the stacked sheets 6 together with the pallet 4 is discharged outside. Then, the sheet delivery table 26 on which another new pallet 4 is placed for replacement is lifted to stop at a predetermined height. A sheet stopper 32 is operated so as to regulate rear ends of the sheets 6 and at the same time, the shutter bar unit 12 is retreated to the stand-by position so that the provisionally received sheets 6 are placed on the pallet 4. Thereafter, the sheet delivery table 26 is lowered corresponding to the thickness of the falling sheets 6 and the sheets 6 are stacked one after another on the pallet 4.
On the other hand, in the divided stacking system shown in FIG. 8(b), a partition plate 35 is inserted between the sheets 6 above the pallet 4 so that the sheets 6 are separated into bundles of the stacked sheets, wherein each of the bundles contains a predetermined number of the sheets 6 and is stacked one on another with a predetermined gap being maintained between the partition plate 35 and an upper surface of the bundle, as will be described below. This system is often employed when of sheets of thin paper are used or the printing is liable to cause ink transfer on the back-side of the sheet, since the load of the weight of the stacked sheets 6 can be separated into smaller units.
In the divided stacking system, as shown by a sheet stacker 3′ of FIGS. 10(a) and 10(b), there is provided a plate receiving device 33 comprising rails 34a, 34b. While the conveyed sheets 6 are falling down in operation, the sheet delivery table 26 is lowered to a predetermined position and the partition plate 35 is quickly moved on the rails 34a, 34b so as to be inserted between the falling sheets 6 and the stacked sheets 6 on the sheet delivery table 26 portion. Thereby, the sheets 6 are separated into a lower bundle of the stacked sheets 6 and an upper portion of the subsequent sheets 6 to be stacked.
The two rails 34a, 34b of the plate receiving device 33 are provided in parallel to the sheet conveying direction of the sheet conveyor 2 above both sides of the sheet delivery table 26, pallet 4, partition plate 35 and stacked sheets 6 and are constructed to be moveable in a back and forth direction to a center of the sheet delivery table 26 so that a distance between the rails 34a, 34b is changeable.
After the (new) partition plate 35 is so inserted between the sheets 6, blocks 36 are put in between four corner portions of the new partition plate 35 and those of the previous partition plate 35. The sheet delivery table 26 is slightly lifted and the rails 34a, 34b are moved toward outside in the width direction of the sheet conveyor 2 so that the new partition plate 35 is completely supported by the blocks 36 resting on the previous partition plate 35. The height of the blocks 36 is set to be slightly higher than the thickness of the stacked sheets 6 so that a gap d is formed between a lower surface of the partition plate 35 supported by the blocks 36 and an upper surface of the stacked sheets 6. Thereafter, the same operation is repeated and bundles of the sheets in which each bundle has a predetermined number of sheets are sequentially formed.
While the conveyed sheets 6 continue to fall down, when the total weight of the stacked sheets 6 on the sheet delivery table 26 reaches a predetermined level, the sheet delivery table 26 is slightly lowered and the partition plate 35 is inserted between the sheets 6 at a high velocity. Thereby, the sheets 6 are separated into the upper bundle supported by the new partition plate 35 and the lower bundles supported by the previous partition plates 35. Then, the sheet delivery table 26 is lowered to the lowermost position to stop there and the bundles of the stacked sheets 6 together with the pallet 4 are discharged outside.
Then, the sheet delivery table 26 is lifted to a predetermined height position to stop there, the pallet 4 is placed on the sheet delivery table 26 and the rails 34a, 34b are moved aside. The sheet delivery table 26 is lowered corresponding to the thickness of the sheets 6 being stacked and thus the predetermined number of the sheets 6 are stacked on the pallet 4. Thereafter, the above-mentioned operations are sequentially repeated.
In the prior art sheet delivery device 1 of a sheet-fed press, while the sheet stacker 3 is constructed to function as mentioned above, there are structural shortcomings, as mentioned next, in the case of the continuous stacking system shown in FIGS. 9(a) and 9(b):
(1) As the shutter bar unit 12 is inserted between the stacked sheets 6 and the sheets 6 that are being conveyed at a high velocity, there is a risk that the falling sheets 6 are crushed by the shutter bar unit 12.
(2) Unless the crushed sheets (spoilage) 6 are immediately removed, there is caused an obstacle in stacking the subsequent sheets 6. But the removing work thereof accompanies dangers because there are nearby rotating machines and devices. Also, stacking (jogging) of the falling sheets 6 may be affected by the removing work.(3) While the shutter bar unit 12 is being operated, the velocity of the printing must be lowered and this remarkably deteriorates the production efficiency.
In order to overcome the above-mentioned shortcomings, while there are proposed such a structure that the drive mechanism of the shutter bar unit 12 is improved to elevate the moving velocity (the Japanese patent laid-open application Hei 9-309660, page 2, FIGS. 1 and 2, for example), etc., there are still problems in the complicated structure of the stacker, etc.
In the case of the divided stacking system shown in FIGS. 10(a) and 10(b) also, like the continuous stacking system, there are structural shortcomings as follows:
(1) As the partition plate 35 must be quickly inserted between the stacked sheets 6 and the sheets 6 that are being conveyed to fall down at a high velocity, there is a risk that the falling sheets 6 are crushed by the partition plate 35.
(2) Unless the crushed sheets (spoilage) 6 are immediately removed, there is caused an obstacle in stacking the subsequent sheets 6. But the removing work thereof accompanies dangers because there are nearby rotating machines and devices. Also, stacking (jogging) of the falling sheets 6 may be affected by the removing work.(3) While the partition plate 35 is being inserted, the velocity of the printing must be lowered and this remarkably deteriorates the production efficiency.
Also, as a common problem for both systems, highly skilled operators are needed. Further, in the prior art sheet delivery device 1 portion, there is disclosed no such device yet as having both of the shutter device 11 as shown in FIGS. 9(a) and 9(b) and the plate receiving device 33 as shown in FIGS. 10(a) and 10(b). That is, in the prior art sheet delivery device 1, the shutter device 11 is provided only in a press exclusive for the continuous stacking system and no shutter device 11 is used yet for the divided stacking system.